61. Rotate List**

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:
Given 1->2->3->4->5->NULL and k = 2,

return 4->5->1->2->3->NULL.

    public ListNode rotateRight(ListNode head, int k) {        if(head ==null||head.next==null) return head;        ListNode dummy = new ListNode(0);        dummy.next = head;        ListNode fast = dummy, slow = dummy;                int length;        for(length = 0; fast.next!=null; length++){            fast = fast.next;        }        for(int j= length-k%length;j>0;j--){            slow = slow.next;        }        fast.next = dummy.next;        dummy.next = slow.next;        slow.next = null;        return dummy.next;    }

总结：dummy节点的引入，很常用。另外注意循环移位要进行取余数处理。